Rockets or Space Planes?

[swjr-swis]

16 hours ago, Andrew Ridgely said:

Which do you prefer?  Rockets or Space Planes?

*breathe* I find your lack of imagination disturbing. *breathe*

Why not stations, or bases, or rovers, or flying bricks, or crazy rivers, or statues, or cows, or trebuchets, or trebuchets launching cows, or pitch forks, or piston engines, or TIE fighter, or constellation class starships, or ...?

You don't know the power of the Da.. I mean, the KSP sandbox. Use the force, dude.

[Jarin]

Just now, Brainlord Mesomorph said:

My planes have parachutes and often splashdown. (i'm too lazy to land them )

Really pushing the definition of "plane" here. I suspect there's plenty of craft that mostly fall under the category of "rocket" that could glide with body lift.  

[Brainlord Mesomorph]

3 minutes ago, Jarin said:

 

4 minutes ago, Brainlord Mesomorph said:

My planes have parachutes and often splashdown. (i'm too lazy to land them )

Really pushing the definition of "plane" here. I suspect there's plenty of craft that mostly fall under the category of "rocket" that could glide with body lift.  

 

really?

[Diche Bach]

5 minutes ago, swjr-swis said:

*breathe* I find your lack of imagination disturbing. *breathe*

Why not stations, or bases, or rovers, or flying bricks, or crazy rivers, or statues, or cows, or trebuchets, or trebuchets launching cows, or pitch forks, or piston engines, or TIE fighter, or constellation class starships, or ...?

You don't know the power of the Da.. I mean, the KSP sandbox. Use the force, dude.

I'm probably going on to thin ice posting TWO humorous (well, that is the _intent_ anyway . . .) Youtubes in the same thread, but your wondrous Francophone insights are too inspiring not to remind us all of the wonders of early medieval "cow flight" technology . . .

 

[Jarin]

1 minute ago, Brainlord Mesomorph said:

really?

That can fly and land on its own. The parachute is for emergencies.

[tater]

11 minutes ago, Jarin said:

The Space Shuttle was an ungainly and inefficient mess.

I guess it has to boil down to "horizontal landing" as the dividing line, then?

This is kind of my feeling on the matter, but I suspect I'd have an uphill climb to make that argument stick.

In which case Gemini with a parasail was a spaceplane?

I honestly do not consider Shuttle/Buran/X-37/Dreamchaser, etc to be spaceplanes.

I'm not sure if a "real" spaceplane should have to take off horizontally, or if it merely have to generate some % of its altitude gain in the atmosphere via lift. Its certainly hard to nail down.

[Jarin]

2 minutes ago, tater said:

In which case Gemini with a parasail was a spaceplane?

Yeah, once you give up the qualification of "can handle sustained horizontal flight at TWR < 1" you get silliness like this.

[Brainlord Mesomorph]

2 minutes ago, Jarin said:

That can fly and land on its own. The parachute is for emergencies

Exactly just like mine. But sometimes my definition of emergency is: I'm 50 m over the runway and its dinnertime.

[Jarin]

2 minutes ago, Brainlord Mesomorph said:

Exactly just like mine. But sometimes my definition of emergency is: I'm 50 m over the runway and its dinnertime.

Then you're just fine in the spaceplane definition. Pretty sure I said "can" not "always has to".

Edit: didn't say either, but whatever, it's capability we're discussing. Pointing my spaceplanes vertical doesn't make them rockets.

Edited September 7, 2016 by Jarin

[Red Iron Crown]

19 minutes ago, Diche Bach said:

So one more tangential question  . . . I reckon we all put "fins" on our "rockets." So why are those not "wings?" I guess they do not provide the lift that allows the craft to maneuver below TWR < 1 so they don't count as "wings?"

But then . . . the "wings" on the Buran, Space Shuttle etc. definitely do not provide enough lift for those vehicles to behave like say . . . an airliner (even on their return trip when they have used most of their fuel, let alone when they launch). Once they are on descent, they're options in terms of changing their trajectory and descent profile are fairly narrow in range no?

I think the distinction here is that fins are not meant to provide significant lift at any phase of operation, only directional control. The wings on the Buran and Space Shuttle are meant to provide lift during the final stages of descent.

19 minutes ago, Diche Bach said:

Not trying to be a pest, but . . . if I'm on the right track here, it sounds like the Buran and Space Shuttle at least (and maybe the other ones wiki refers to as "spaceplanes") are NOT really spacePLANES so much as "spacecraft-that-can-glide-home?"

One could certainly define it that way, I suppose.

19 minutes ago, Diche Bach said:

Wrapping this up: I am under the impression that humanity (in real life) has yet to build a vessel that can take off from a runway, function within the operational zone of say a B-52 or big airliner (major trajectory and pitch changes, moderate manuverability, can reland at any time it likes if necessary and under it's own propulsive power) AND can at an early stage in its mission, ascend to orbit, then descend back to landing (under it's own propulsive power and not simply gliding).

None built yet. Skylon will meet these requirements if it is ever built and performs as advertised, and there have been other, similar concepts in the past.

19 minutes ago, Diche Bach said:

I defer to you guys, but it seems to me, THAT should be the definition of  "spaceplane" = a perfectly functional "airplane" that can also attain orbit and come home safe and sound by runway landing. I realize this is not how the term seems to be used, but it would seem that is how at least some folks on these forums reserve the term, and it does seem to capture a variant that is distinct from the others.

By that definition the X-15 and SpaceShipOne/Two are not spaceplanes, whereas I think most people would consider them as such.

[KerikBalm]

37 minutes ago, Jarin said:

That seems to be the order of the day.

I like the TWR comment though, with one exception. *CAN* fly with TWR < 1, rather than simply has that. Every SSTO spaceplane I fly has TWR > 1 once the engines hit their optimal range, even if they didn't start that way. 

Well, in my comment, I did say can... " can/does fly with a TWR < 1 "

31 minutes ago, Brainlord Mesomorph said:

The Space Shuttle fails that definition.  (Or are you considering dead-stick gliding as flying)

Yes, I would. It is in stable aerodynamic flight where the force of lift cancels the force of gravity... but now we're into a definition of flying... a brick at terminal velocity meets the definition of aerodynamic forces meeting equalling the force of gravity, such that there is no net acceleration in the vertical direction...

But we can define lift as the aurodynamic force perpendicular to the direction of motion... so an object falling straight down at terminal velocity doesn't count...

Anyway, considering that I fly hang gliders... I sure as heck want unpowered gliding to be considered flight

Spoiler

But then... wingsuiters fly too under that definition... and anything that lands under a paraglider type canopy does too (granted it would only be the upper stage, the lower stages would still fail that definition.

Anyway... I like to think of a space plane as something that is acting as a plane (using aerodynamic lift to counteract gravity) as an integral part of reaching space... not just acting as a plane when the "space" part is over.

But that's just me, not a commonly accepted definition (and yes, that definition would exclude the space shuttle, and especially the X-37 that rides to space inside a fairing)

[Daveroski]

A space-plane can take-off like an aeroplane.

If it doesn't take off like an aeroplane it isn't a space-plane.

 

It has wing surfaces and uses atmospheric lift like an aeroplane.

If it doesn't have wing surfaces and use atmospheric lift then it isn't a space-plane.

 

It has to be able to make orbit.

If it can't make orbit it isn't a space plane.

 

It has to be able to land on a runway.

If it can't land on a runway, it isn't a space plane.

 

It has to be able to do all of these things in a single flight.

If it can't do all of these things in a single flight it isn't a space-plane.

Finally, it must be able to do all of theses things in a single stage.

No matter how much it hurts your feelings, if it can't do all of these things in a single stage it is not a space-plane.

You could call a submarine a 'ship' and have a submariner slap you upside the head for doing so because it isn't a ship.

Just as some things can do some of the things a space-plane does does not make it a space-plane.

It must be able to do them all.

Live with it.

 

Edited September 7, 2016 by Daveroski
Typo

[tater]

And strictly speaking, "lift" cannot be part of the definition if the only part of the flight where it is used is EDL, as Apollo capsules (and current capsules) use lift.

2 minutes ago, Daveroski said:

Clipped for length.

It need not be SSTO to be a spaceplane. Some of the original Shuttle concepts were legit spaceplanes, but they were TSTO designs.

[Red Iron Crown]

3 minutes ago, tater said:

And strictly speaking, "lift" cannot be part of the definition if the only part of the flight where it is used is EDL, as Apollo capsules (and current capsules) use lift.

What if "lift generating wings" are part of the definition?

[tater]

3 minutes ago, Red Iron Crown said:

What if "lift generating wings" are part of the definition?

Define "wings."

Did X-15 have wings, or fins? HL-10? X-24? What about lifting body designs? What % of lift must be generated by the cantilevered bits for them to stop being fins?

Edited September 7, 2016 by tater

[Jarin]

8 minutes ago, Daveroski said:

Live with it.

No.

[MaverickSawyer]

Why not both?

Rockets are better for early career and heavy payloads that have to be launched in a single shot, buy spaceplanes are more flexible in later career and can (in the long run) cheaply be used for repeated flights, like assembling a Jool 5 mission or a Grand Tour ship.

[Red Iron Crown]

5 minutes ago, tater said:

Define "wings."

Did X-15 have wings, or fins? HL-10? X-24? What about lifting body designs? What % of lift must be generated by the cantilevered bits for them to stop being fins?

I'm just going to have to say, with apologies to Potter Stewart: I shall not today attempt further to define the kinds of craft I understand to be embraced within that shorthand description "spaceplane"; and perhaps I could never succeed in intelligibly doing so. But I know one when I see it.

[suicidejunkie]

10 minutes ago, Jarin said:

The Space Shuttle was an ungainly and inefficient mess.

I guess it has to boil down to "horizontal landing" as the dividing line, then?

This is kind of my feeling on the matter, but I suspect I'd have an uphill climb to make that argument stick.

I'm pretty sure someone has built a rolling/horizontal takeoff + tail lander spaceplane.

 

Some rough definitions IMO:

SSTO: If your contraption achieves orbit with exactly the same parts as it had when it first started moving.  (launch clamps don't count)

-Rocket-: uses "main" engines with internal propellant (jets don't count, RCS usually doesn't count but a pack of linear thrusters on the back could)

-Space-: exceeds 70km altitude.  Often replaces 'rocket' where applicable.

-Plane-: aerodynamic lift can be greater than craft weight for an extended period of time.

V/H TO/L: combinations to indicate vertical or horizontal take offs and/or landings.

[tater]

I'd not include suborbital craft at all, it muddies the waters since suborbital is pretty much useless.

[Kerbinchaser]

I have never used a spaceplane, and intend to never use them. Most missions I do are by rocket.

[pandaman]

I tend to do rockets most of the time.  But I enjoy using shuttles and trying to design spaceplanes for a change or the challenge depending on my mood and what I'm doing. 

[The_Rocketeer]

I think everybody knows what a plane is, right?

Well, a spaceplane is basically one of those that can go to space.

[legoclone09]

I have come with a solution!

[UnusualAttitude]

1 hour ago, Diche Bach said:

Wrapping this up: I am under the impression that humanity (in real life) has yet to build a vessel that can take off from a runway, function within the operational zone of say a B-52 or big airliner (major trajectory and pitch changes, moderate manuverability, can reland at any time it likes if necessary and under it's own propulsive power) AND can at an early stage in its mission, ascend to orbit, then descend back to landing (under it's own propulsive power and not simply gliding).

Just to give you an idea what this takes in RSS:

This is a spaceplane (as you define it) that can lift 15 tonnes to Low Earth Orbit. It is made from procedural tanks, wings and parts from Nertea's MkIV mod.

The dual cycle main engines are completely made up: they burn liquid methane and to get it to SSTO I had to give them a TWR of 50. Now, there are RL rocket engines with better TWR than this, but remember they don't need a pre-cooler or an air intake. So, ambitious, but maybe not impossible. I've simply no idea how heavy the pre-cooler should be.

In terms of fuel fraction: this is where things get a bit far out. Take-off weight is 350 tonnes, empty weight is 37 tonnes. That's almost as good as a rocket, and remember this thing needs wings, control surfaces, landing gear, etc... So perhaps not as ambitious as a space elevator, but pretty damn hard.

Note that REL quotes an empty weight of 53 tonnes for Skylon, for a take off weight of 325 tonnes. But its fuel (liquid hydrogen) is lighter.

To get back on topic: do I spaceplane? Yes, even in RSS. Because it's fun.